A rotating distributor of this type is disclosed in the document FR 2 791 598 in the name of the applicant. By referring to FIG. 1 of the accompanying drawings, the rotating distributor, denoted in its entirety by the reference numeral 1, comprises two coaxial rings 2, 3, in principle with substantially vertical axis A in the conditions of use as shown in FIG. 1. One of the rings (the ring 2 located below in FIG. 1) is fixed and the other ring (the ring 3 located above in FIG. 1) is rotating. They are sealingly in contact against one another by means of respective opposing contact faces 4, 5 defining a joint plane P. The rotating ring 3 comprises communication orifices, generically denoted by the reference numeral 6, which are each adapted for being connected to at least one individual treatment station for a container and which open onto the contact face 5 of said rotating ring 3. The fixed ring 2 comprises at least one aperture, generically denoted by the reference numeral 7, which is adapted for being connected, at 8, to a pressure source of the machine and which opens onto the contact face 4 of said fixed ring 2 so as to be located on the trajectory of the orifices 6 of the rotating ring 3; in this manner a treatment station is connected to the pressure source when the corresponding orifice 6 is coincident with the aperture 7. Finally, grease is spread between the respective contact faces 4, 5 of the two rings 2, 3 to prevent dry friction of the face 5 of the rotating ring 3 on the face 4 of the fixed ring 2, but also, and primarily, to provide the seal of the contact of the two faces 4, 5 and thus the seal of the connections between the aperture 7 and the successive orifices 6, with regard to the pressure.
In the design thereof as disclosed and shown in the document FR 2 791 598, the rotating distributor 1 is designed with orifices 6 for connecting to the treatment stations which are distributed over two circumferences, generically denoted by the reference numeral 9, of different diameters (the orifices located on said two respective circumferences 9e, 9i, are denoted respectively 6e, 6i) and with at least two apertures 7e, 7i for connecting to at least one pressure source which are also located on two circumferences of the same diameter as those of said orifices 6e, 6i. This arrangement is clearly seen in FIG. 2 of the accompanying drawings which is a view from below of the rotary ring 3.
In this known arrangement, the orifices 6 and apertures 7 of the respective rings 2, 3 are radially spaced apart from the external and internal peripheral edges, respectively 10e, 10i,11e, 11i, of the two rings 2, 3. In the embodiment of the rotating distributor 1 illustrated in FIG. 1, the two rings 2, 3 have substantially the same diameter and the orifices 6 of the rotating ring 3 have substantially the same diameter or at least the same radial dimension as the apertures 7 of the fixed ring 2. As a result, the orifices 6 and the apertures 7 are located at the same radial distance De from the edges 11e, 10e of the respective rings 3, 2 and at the same radial distance Di from the respective edges 11i, 10i of the rings 3, 2. In the example shown, the radial distances De and Di are substantially equal, as is seen more clearly in the representation of the rotating ring 3 in a view from below provided in FIG. 2. Moreover, in this example, the distances De, Di are of the same size as the internal diameter of the orifices 6 of the rotating ring 3 as is seen in FIG. 2.
Thus the respective widths De, Di of the seals formed by the lubricant on the external and internal peripheries of the joint plane P are sufficient to provide the required seal.
This known arrangement is currently used in rotating machines typically having 20 treatment stations, and it is completely satisfactory.
However, manufacturers of containers and in particular bottles wish to increase the rates of production in a permanent manner. For certain treatments (for example the depositing of a barrier layer of carbon on the internal face of containers made of thermoplastic material such as PET by using a low pressure plasma), the speed of the sequence of the treatment process in the region of each station may not be significantly increased. A significant increase in the rate of production may thus only be envisaged by increasing the number of treatment stations. It is in this manner that the applicant envisages to develop a new machine in which the number of the treatment stations is markedly increased, typically almost doubled.
In regard to the rotating distributor, this may be translated by a corresponding increase in the connections to be provided, i.e. typically by almost doubling the number of communication orifices to be provided on the rotating ring.
However, the rings of the rotating distributor are pieces of large size which are very heavy; typically, in current machines equipped with 20 treatment stations, the rings have a diameter of approximately 0.60 meters and an individual weight in the order of 110 kg. Whilst it is possible to increase the external diameter slightly further, the capacity of the machines required for the manufacture of these rings nevertheless imposes a limit which it is not possible to exceed, which however would be necessary to distribute the increased number of communication orifices over the same number (typically two) of circumferences of different diameters. So that the rings maintain approximately their current diameter, it is therefore necessary to distribute the communication orifices over a greater number (typically three, even four) of circumferences of different diameters.
This object is possible to achieve, for example, by reducing the diameter d of the central recess 12 of the rings 2, 3 and by occupying to a maximum extent the available surface in the rings. This results in arranging the orifices 6 and the apertures 7 located on the respectively external and internal extreme circumferences 9e, 9i, as close as possible to the respectively external and internal peripheral edges 10e, 11e, 10i, 11i, of the rings 2, 3. By way of example, FIG. 3 shows in a view from below a rotating ring 3 designed according to a configuration of this type with the orifices 6 distributed in three groups 6e, 6m, 6i, located respectively on three circumferences 9e, 9m, 9i, respectively external, median and internal.
Nevertheless, in this case, the distances De′ between the external edges of the orifices 6e and the external edge 11e of the ring 3 and Di′ between the internal edges of the orifices 6i and the internal edge 11i of the ring 3 (and similarly for the fixed ring 2) are considerably reduced (typically by approximately 49 mm over the current machines) and as a result the widths of the lubricating joints on the external and internal peripheries of the joint plane become insufficient to provide the required seal.